Interlocking joint for collapsible structures



June 17, 1969. o. SEDA ETAL 3,450,293

INTERLOCKING JOINT FOR COLLAPSIBLE STRUCTURES Filed Sept. 26, 1967 INVENTORS 0 944 100 A. @504 BY SELE/YA 9000540 United States Patent US. Cl. 220--4 Claims ABSTRACT OF THE DISCLOSURE This invention is directed to a collapsible box-like structure, such as an electrical chassis box or minibox, having unique interlocking members. Each side plate has a generally C-shaped flange at one end, which opens inwardly toward the center of the plate and a generally tilted J- shaped flange at the other end, which opens outwardly away from the center of the plate, i.e. L1. The C-shaped flange of each of the four side plates meshes and interlocks with the J-shaped member of each said side plate adjacent thereto. The interlocking flange members at their bottom lips form a generally circular opening for the insertion of a fastening member which tightens the joints between the side plates and provides a means for attaching face plates to close the box-like structure.

Background Box-like structures with collapsible plates come in many sizes and shapes with different degrees of sophistication in the manner by which the plates are joined or fastened. These box-like structures have been found useful in many industries. In the electronics industry a wide variety of such structures have been devised to serve as chassis and shielding enclosures. These are suitable for housing as semblies above-chassis or below-chassis. Shielding enclosures are suitable for preventing undesirable coupling in audio and radio frequency circuits; for these self-com tained units protection from dust and dirt is also desirable.

Small enclosures of this type, commonly referred to as miniboxes, are available as stock items for the housing of electrical circuitry. These miniboxes are popular with electronics laboratories, vradio amateurs, broadcast studios and many others who have a need to house circuitry from the infinite variety generated each year by the electronics industry.

Typically, the minibox is formed of sheet metal in the shape of two U-shaped channels with overlapping edges which interlock; this construction has been standard for many years. This type of minibox is of realtively crude construction, with ill-fitting tension joints which loosen upon use. They are diflicult to cut, punch and drill for the mounting of electronic components. In addition, the insides of the channels are relatively inaccessible, presenting problems of wiring components and of access to circuitry for servicing.

Box-like systems with collapsible sides provide greater access and versatility, but result in the sacrifice of simplicity to achieve this. In particular the variety of dove tail, ball and socket, tongue and rabbet, and spline joints which might be considered require either metal plates that are too thick to be practical, or the joints consume too much room within the structure or the structures are not sufiiciently sturdy or economical. The use of crimped brackets, or external or internal clamps to join panel members has not proven to be entirely satisfactory.

In view of these disadvantages a need exists for an improved box-like structure which is suitable for numerous diverse uses. Such a structure should be tight and rigid;

readily assembled and disassembled, and easily manufactured.

The invention It is therefore an object of this invention to provide an improved box-like structure with collapsible side walls and interlocking joints. This has been achieved by the fabrication of side plate members having depending flanges which form longitudinally extending grooves along two opposite edges of each plate. A first flange on each plate curves downwardly, from a point near a first edge and terminates in a lip toward the center of the plate. A second flange curves downwardly from a point inward from a second edge and terminates in a lip away from the center of the plate. The opening of each groove formed by these flanges is sufficiently wide to have inserted therein the lip from the flange of an adjacent plate. Therefore the first flange on a first plate which curves inwardly interlocks with a second flange from a second plate which curves outwardly, and the second flange of said first plate which curves outwardly interlocks with a first flange from a third plate which curves inwardly. In this manner four duplicate plates interlock to form an open box-like structure. The interlocking flanges are shaped in a manner to form a generally circular opening into which a fastening member can be placed to tighten the joints or by which face plate members can be attached to close the structure.

Further details and additional aspects of this invention will become apparent by reference to the following detailed description when considered in conjunction with the appended drawings, wherein:

FIGURE 1 depicts the overall configuration of a sixpiece box-like structure;

FIGURE 2 illustrates in greater detail the configuration of the interlocking members at a corner of the structure; and

FIGURE 3 shows the detailed configuration of a plate member suitable for use in this invention.

The enclosure of FIGURE 1 comprises six removable plate members. Side plates 1, 2, 3 and 4 are constructed to interlock in accordance with the present invention. The nature of the interlocking portions are described in greater detail below. Plate 4 shows the optional configuration of a conventional finned plate which facilitates heat transfer, for example, when the enclosure is used for electrical components. Face plate 5 is fastened to the structure by means of fasteners 7, 8, 9 and 10 through corresponding holes 11, 12, 13 and 14 of plate 5. The fasteners, as depicted, are screw-type; however, wedge, bolt or nailtype fasteners may also be used, as will be evident from the function of these members. A similar construction (not shown) is provided to fasten plate 6 to the structure formed by interlocking plates 1, 2, 3, and 4.

In FIGURE 2 the details of the interlocking edges of plates 1 and 2 are shown. The lower portion of plate 1, shown as 1A, comprises a depending curved member 15 which interlocks with the depending curved member 16, which projects from the righthand portion of plate 2, shown as 2A. Member 15 will be referred to as generally J-shaped and member 16' as generally C-shaped. At 1A a recess is provided in the plate to receive C- shaped member 16. Similarly, a recess is provided at 2A to receive the J-shaped member 15. Although recesses have been shown at 1A and 2A to receive the curved members of the adjacent plate, the plate members could be made with a more uniform thickness. This is illustrated by the broken lines which signify the boundaries of plates 1 and 2 with sections 1B and 2B removed. At 2A there is also provided an optional projecting member 17 which abuts member 15. Interlocking members 15 3 and 16 form a recess which receives fastener 10 and is aligned with hole 14 of plate 5 (see FIGURE 1).

When an open-ended enclosure is desired, such as without face plates 5 and 6, or when an alternative method of securing the face plates is used, the fasteners 7, 8, 9 and 10 may be eliminated. The interlocking members and 16 or 15, 16 and 17 provide a suitable joint. However, it has been found that the use of fasteners, such as 10, produces an unusually strong and tight joint. For example the use of a screw fastener produces a torsional tightening effect which firmly wedges the curved members 15 and 16 into their respective adjacent plates, as indicated generally by the curved broken arrows. Moreover, additional lateral forces are produced to further tighten the joint, as indicated generally by the straight broken arrows. A similar effect can be produced by other types of fasteners which wedge the curved members against each other and their adjacent plates.

Curved members 15, 16 and 17 may extend along the entire length of their respective plate members (note, for example, the joint structure between plates 2 and 3 in FIGURE 1). Alternatively these curved members may be discontinuous and divided into mating segments along the length of the plate members, or could extend for only a short distance inwardly near each of the open ends or face plates. For miniboxes, particularly when fabricated by extrusion, the preferred embodiment is that shown in the drawings, such as FIGURE 1. Moreover, as is evident from the self-contained joint of FIGURE 2, not only may the face plates be omitted to form a 4-sided structure, but one or more of the side plates may be omitted. For example, FIGURE 2 illustrates an L-shaped structure in which flanges may be fabricated for the joint at ends 1A and 2A only. Alternatively, U-shaped members may be formed by using a central plate with flanges on each end, and two side plates with flanges on only one end, or three of the four side plates of FIGURE 1 may be used to form a U-shaped structure, with or without face plates. Many such alternatives are available in which advantageous use may be made of the interlocking joint of FIGURE 2.

The preferred embodiment for maximum strength and ease of manufacture, is that in which each of the side plates is constructed as shown in FIGURES 1 and 2, as set forth in detail in FIGURE 3. The interlocking portions of each of plates 1, 2, 3 and 4 may be as illustrated in this figure. The J-shaped member of one plate interlocks with the C-shaped member of another plate. In FIGURE 3, a typical plate is shown, with a J-shaped member 15', and a C-shaped member 16' and a projecting member 17'. C-shaped member 16' depends from a point 18 adjacent to edge 19 and terminates in a lip 20 inwardly toward the center of the plate or toward opposite edge 21. I-shaped member 15 depends from a point 22 inward from edge 21 and terminates in a lip 23 outwardly from the center of the plate or toward the edge 21. Each of edges 19 and 21 are mitered at a suitable angle, such as 45, to mate with the edges of adjacent plates (as in FIGURE 1). The inner surfaces, 24 and 25, of lips 20 and 23, respectively, have substantially the same radial dimensions R, so that upon meshing of the interlocking flanges a generally circular recess is formed for a fastener, as shown in FIGURE 2. Of course, just as different types of fasteners may be used, other shapes for the recess formed by the interlocking flanges would also be suitable. The only requirement is that the matching fastener and recess produce forces which tighten and strengthen the joints. Adjacent to curved surfaces 24 and 25 are flat surfaces 26 and 27 which, upon interlocking engagement, receive in abutting relation lips from adjacent plates similar to 23 and 20 respectively. These fiat surfaces may be shaped differently to complement the shape of the lip portions which abut them. The radii R R R and R are all equal since in interlocking engagement the inner surface at R is abutted by a surface similar to R from an adjacent plate whereas inner surface R is abutted by a surface similar to R from an adjacent plate. The opening to the groove formed by J-shaped flange 15 is defined by the distance between the lip 23 and the lower portion of edge 21. This opening must be sufficiently wide to accommodate the width of the C-shaped member of an adjacent plate. Similarly, the openingto the groove formed by C-shaped flange 16' is defined by the distance between the lip 20 and projecting member 17'. This opening must be snfliciently wide to accommodate the width of the J-shaped member of an adjacent plate.

One advantage of the present invention is that the labyrinth path of the joint provides a substantially moisture-proof seal. The joint system may be further waterproof by providing an elastomeric spline along the length of the joint.

In the design of a minibox in accordance with the present invention, FIGURE 3, which is to scale, may serve as an example. The length of a plate may be 2 inches with a thickness of 0.1 inch. Radii R may be slightly under 0.05 inch and radii R R R and R may be 0.1 inch. The center for these radii may be 0.163 inch down from the top of the plate and inward from the edges. Flat surfaces 26 and 27 are perpendicular to the 45 edges 19 and 21.

The minibox may of course be provided with punchouts or holes (not shown) for electrical leads or mounting purposes. Miniboxes or other electrical housing structures may be provided with one or more side plates (or face plates) having a finned exterior (plate 4, FIG- URE 1) to increase the surface area and improve the transfer of heat through the housing, from components mounted on the inside of the box, to air passing over the outside of the box. The minibox structure may be fabricated from aluminum by extrusion, although other metals and fabricating techniques are suitable.

Larger structures than miniboxes may of course be constructed in accordance with the present invention. The miniboxes or larger structures may have square or rectangular cross-sections. In one embodiment of this invention grooves may be provided to accommodate panels within the box-like structure of FIGURE 1. A panel for compartmentalization or support of circuitry may be inserted into the structure of FIGURE 1 and supported by grooves or clips in opposing side walls. As illustrated in FIGURE 3 each plate member may be provided with a conventional groove 28, defined by the broken lines, for the support of such panels.

Alternatively, the interlocking joints of the present invention may be utilized for the support of panels. In FIGURE 3, C-shaped member 16" and member 17" would be provided to mesh with a panel having a J- shaped flange. A side plate in a structure opposite the plate of FIGURE 3 could have a C- on I-shaped flange similarly positioned to mesh with a I- or C-shaped flange on a panel member. Fastener means could also be used with such intermediate panel members and the face plates could be provided with corresponding holes for such fasteners.

The structural members of this invention may be formed of any suitable material, metallic, or non-metallic, such as plastics. The preferred structural members for electrical purposes are of .aluminum. Iron-based members such as cast iron, and steel are also useful in the present invention.

The invention has been described in terms of specific embodiments set forth in detail, but it should be understood that these are by way of illustration only and that the invention will become apparent to those skilled in the art in view of this disclosure, and accordingly, modifications of the product disclosed herein are to be contemplated within the ,spirit of this invention.

What is claimed is:

1. A collapsible metal enclosure comprising four adjacently members,

and perpendicularly positioned interlocking each of said interlocking members having a first and second flange which form a first and second longitudinally extending groove at opposite edges of said interlocking members,

said first and second flanges being respectively defined by a first and second curved member,

said first curved member, being generally C-shaped and depending from a point adjacent to a first edge of said first interlocking member and terminating in a lip directed toward the opposite second edge,

said second curved member being generally J-shaped and depending from a point inward from said second edge and terminating in a lip directed toward said second edge,

said first flange on each of said interlocking members being adapted to interlock with said second flange on an adjacently positioned interlocking member,

recesses on each end of said interlocking members approximately opposite said lips of said curved members and adapted to receive and abut said curved member on an adjacently positioned interlocking member,

each of said interlocking members terminating in an edge adapted to abut a corresponding edge of an adjacently positioned interlocking member.

2. The enclosure of claim 1 wherein said O and J- 3. The closure of claim 2 comprising two face plates removably secured to said enclosure by said fasteners to provide a completely closed structure.

4. The enclosure of claim 1 wherein at least one of said interlocking members has a finned exterior.

5. The enclosure of claim 1 wherein said interlocking members are made of a metal selected from the group consisting of aluminum and iron-based metals.

References Cited UNITED STATES PATENTS 2,816,070 12/1957 Buchanan 22072 X 3,092,962 6/ 1963 Wood. 3,302,814 2/1967 Dohner 220 X FOREIGN PATENTS 12/1903 France. 11/1964 Austria.

GEORGE E. LOWRAN CE, Primary Examiner.

US. Cl. X.R. 

